1. Field of the Invention
The present invention relates to a standby process controller and a standby process control method of an electronic device, and is particularly suitable for a device which controls the operations of an activation process (a standby-out process) performed when the power of the electronic device is turned on and an end process (a standby-in process) performed when the power of the electronic device is turned off.
2. Description of the Related Art
In general, when the power of the electronic device in a standby state is turned on, a predetermined activation process (the standby-out process) is performed, and the electronic device enters an operable state. On the other hand, when the power of the running electronic device is turned off, a predetermined end process (the standby-in process) is performed, and the electronic device enters the standby state. The activation process and the end process (hereinafter, both processes will be referred to as “standby process”) have no direct relation to a user's operation on the electronic device. Therefore, it is desirable to perform both processes in a time as short as possible.
For example, there is known a technique of preventing a delay in a soft activation when data is not normally updated and then an ACC (accessory) of the in-vehicle device is turned on (see JP 2013-84089 A). In the technique disclosed in JP 2013-84089 A, a CPU is activated without waiting for an activation factor when the backup of the data is not normally ended, and a memory is shifted from an “idle” state to a “tran” state (a CPU accessible state), so that the memory is already in the “tran” state at the time when the data is normally back up and then the ACC is turned on.
By the way, once the standby process is started, the standby process is not stopped during its operation but performed to the end. In other words, even when the power is switched to be turned on in a period before the process is completed after the standby-in process is started according to the turning-off operation of the power of the electronic device, the standby-in process is performed to the end, and then the standby-out process is started. Similarly, even when the power is switched to be turned off in a period before the process is completed after the standby-out process is started according to the turning-on operation of the power of the electronic device, the standby-out process is performed to the end, and then the standby-in process is started.
Therefore, for example, in a case where the user wants to use the electronic device again by turning on the power within several seconds after the user turns off the power of the electronic device, it takes a considerably long time until the electronic device enters an operable state after the standby-out process is completed. FIG. 8 is a diagram for describing the problem.
In FIG. 8, an ACC signal indicates a signal of turning on/off the power (accessory), and a high state indicates a power ON and a low state indicates a power OFF. A standby-in signal is a signal of instructing the execution of the standby-in process, and is active low. A standby-out signal is a signal of instructing the execution of the standby-out process, and is active low.
As illustrated in FIG. 8, in a case where the ACC-OFF operation is performed when the electronic device is in a normal operation state, the standby-in signal also falls down in synchronization with a falling of the ACC signal, and the standby-in process is started. In general, the standby-in process requires a time of about 5 to 15 seconds. The example of FIG. 8 shows a state in which the ACC-ON operation is performed before the standby-in process is completed.
However, even when the ACC is switched to be turned on during the standby-in process, the standby-in process is continuously performed to the end, and then the standby-out process is started. Then, when the standby-out process is completed, it becomes the normal operation state where the electronic device can be used. Therefore, it takes a considerably long standby time until the electronic device enters an operable state after the ACC is turned on.
In addition, in the electronic device mounted on a specific vehicle, when the ACC-ON operation is performed, the ACC signal is configured to rise and then fall down once, and thereafter rise again as illustrated in FIG. 9. In this case, after the standby-out process is performed to the end according to the first rising of the ACC signal, the standby-in process is performed to the end according to a falling of the ACC signal. Further, the standby-out process is performed again to the end according to the next rising of the ACC signal, and finally the electronic device enters the operable state. Therefore, it takes a considerably long standby time until the electronic device enters the operable state after the ACC-ON operation is performed.
Conventionally, a guard time is set for the electronic device mounted to such a specific vehicle in order to cancel all the signals during several seconds (about 2 seconds) after the first rising of the ACC signal is detected, thereby avoiding a long standby time until the electronic device enters the operable state after the ACC-ON operation is performed.
However, even in such a condition and situation, in a case where the American standard that a captured image of the periphery of a vehicle has to be displayed within 2 seconds after the ACC is turned on is applied to the electronic device, the method of avoiding the standby time using the guard time cannot be employed. This is because even when a signal of instructing the display of the captured image immediately after the ACC is turned on is output, the signal is ignored by the guard time.
The invention has been made in view of the above problem, and an object thereof is to shorten a time taken until an electronic device enters an operable state after a power-on operation is performed.